Electric train signaling system



March 7, 1933. P. N.' BossARTA ELECTRIC TRAIN SIGNALING. SVYSTEM 3 Sheets-Sheet '2 Filed Dec. '3, 1951 T011. Paul N Bossa# Fig.

v HIS AUORNEY.

March 7, 1933. P N BOSSART 1,990,412

ELECTRIOTRAIN SIGNALING SYSTEM Filed Deo. 3, 1931 3 Sheets-Sheetl 3 1N VENTOR. Paal N. Bofssam.

By @fum HIS A TTORNE Patented Mar. 7, 1933 UNITED vsT-.e'rEs PATENT OFFICE :PAUL N. BOSSART, OF SWISSVALE, PENNSYLVANIA, ASSIGNOR 'IO THE UNION SHITCH fr; & SIGNAL COMPANY, OFKSWISSVALE, PENN SYLVANIA, .Ay CORPORATION OF IIENN- sYLvANIA p ELECTRIC 'TRAIN SIGNALING SYSTEM Application. mea December a, 1931. serial n4578545.

My invention relates to communicating systems for railway trains, and has for an object the provision of means for signaling between spaced pointsV on va train, or between two tra-ins, or between the train and a wayside station, that will be substantially immune from interference due to currents flowing in the traflic rails and to foreign' space magnetic fields.

' I will described certain forms of appara# tus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawing, Figs. l and 2 constitute a diagrammatic view of one Y form of apparatus embodying my invention.

Fig. 3 is a magnetic field diagram 'showingl the relationship between the apparatus of my invention and the magneticfields set up about the traflic rails by current flowing in the same direction in the two rails. Fig. 4 is a diagram showing the eect of a current flowing in opposite directions in the traliic rails as far as the apparatus' of my invention is concerned. Fig. 5 is a diagrammatic view showing one method of applying the controlling conductor to a given track layout, while Fig. 6 is a diagrammatic view showing'a sec-- ond method of arranging the controlling conductor to a similar track layout.

Similar reference characters refer to similar parts in each of the several views.

Referring to Figs. 1 and 2 the reference character 2 indicates a conductor fastened to thetop of the ties 3 of a railway approximately halfwaybetween the two traliic rails l and la for the full length of the railway. This conductor 2 should be of suicie'ntly large vsize so that it will withstandA the mechanical abuse it will be subjected to. It vmay 0 or may not be insulated, but it does not need to be. Preferably it should have a resistance not greater than its inductive Areactance at the frequency of the signaling current to be used, but this condition` will in practice always be realized in any conductor having proper mechanical strength; for example, a copper clad steel wire of say one-fourth inch in diameter. Y

When my invention is to be utilized for communicating between two spaced points on the same train, for example, between-the locomotive and the Caboose of a freightA train, the apparatus as indicated at point A in Fig.

'2 will be located onthe locomotive and simi'- A will be on the train and that of B at the wayside station. In the latter case, of course, the wayside apparatus must be installed with proper clearance for all rolling stock ofthe railway. In this case the pick-up coils corresponding tocoils 4 and 5 will be beneath instead of over the conductor 2 and greater efciency can be obtained by positioning them closer to the wire 2 since no clearance below the wire is necessary. I c l 4, 5 and 6 are inductor coils provided at each location and installed in an inductive relation with the conductor 2. 'Ihev coils 4 and 5 are each preferably but not necessarily provided with' a magnetizable core and are mounted with their axes transverse Vto the trackway at an acute angle withthe horizontal plane in such a manner that the/axes intersect approximately at the vertical center line of the trafc track; Coil 6 extends transverse tofthe trackway in a horizontal position but at a considerably greater distance above the conductor`2 than the coils'4 and 5. Coil 6'is necessary only for adjusting against space-uniform fields and is not required lto balance vout currents in the traflic rails. Un'- der'those conditions where practically .all the interference comes from theV traHic rails, coil 6 Vmay be eliminated. `The manner of positioning these coils will be fully Vdiscussed later on vin the specilication. p The coils 4, 5 and 6 are connected in series insuch a manner that the electromotive vforces induced in the coils 4 and 5 by current flowing in theconductor 2 at any given instant williadd their effect/s, while that linduced in coil 6 will oppose that of coils 4 and 5. Likewise, when current is supplied toi-these coils from a local generator to be referred to laterthe two coils 4 and 5 act together to induce an electromotive force in the conductor 2, while the coil 6 due to its connection in the circuit will oppose the influence of coils 4 and 5. The position of coil 6 with respect to the conductor 2, however, will render its infiuence small in comparison with that of the coils 4 and 5 as will appear later. These coils 4, 5 and 6 are connected through a tuning condenser 7 to either a receiving circuitor a transmitting circuit as the case may require. With the contact 8 in the position as shown in Fig. 1 the coils are connected to the input side of alter F through which current is passed to an amplifier AM whose output actuates a loud-speaker LS orl other indicating devices. lVith the contact 8 lowered to its dotted line position the coils 4, 5' and 6 are connected to the output of a generator G of carrier current whose output is preferably modulated in the usual manner by a modulatorM. The frequency of generatorG may be of any convenient frequency, such as five thousand cycles per second. The frequency of the modulator M should be within the audible range if a loud-speaker is to be utilized as the indicating device and in fact when spoken messages are to be transmitted the modulator M will take the form of a voice transmitter and the modulation will be that of the voice frequencies. The filter F, amplifier AM, loud-speaker LS, generator G and modulator M may take any of many well-known forms for such devices and as their Vspecic form constitutes no part of my invention they are. indicated in the drawings diagrammatically only. The contact 8 may be manually operated between its two positions so that an operator can connect the coils 4, 5 and 6 to: either the receiving means or to the transmitting means at will, or contact 8 may be automatically operated and the receiving and transnfiitting means alternately connected to the inductor coils.

The conductor 2 forms Aone side of a closed circuit which is completed through the ground by virtue of the distributed impedance between conductor 2 and ground and the ground path. This distributed impedance between the conductor 2L and the ground is visualized by dotted lines in Fig. 1 by a capacity 10 to ground 9 andaleak resistance 11. The approximate paths taken by the current are indicated by the broken lines of Fig. 2. The manner whereby current induced in a conductor will flow through the closed circuit formed by the distributed impedance and the ground is fully described and claimed inthe L. O. Grondahl application for Letters Patent, Serial No. 450,135, filed May 6, 1930, for electric train signaling system, and it is thought not necessary to repeat the discussion inv detail in the present application. It is to be noted, however, that in the above-mentioned application the two traffic rails in parallel act as the metallic conductor whereas in my system the special Vconductor 2 is employed. In the case where a special conductor such as 2 is employed the shunt capacity 10 is relatively more important than the resistance 11 since the leakage between the conductor 2 and ground will be much less than where the traffic rails are used.

It is apparent, therefore, that with the apparatus at A of Fig. 2 mounted on the locomotive of 'a t-rain and placed in its transL mitting condition, modulated carrier current from its generator AGr will be 'induced in the conductor 2 by means of the coils 4, 5 and 6. This induced current will flow in the closed circuit formed by the conductor 2, the distributed impedance between the conductor and ground and the ground path.4 With the apparatus at B of Fig. 2'placed inits receiving condition the current in conductor 2 will induce an electromotive force in its coils 4, 5 and 6 vwhich-when passed through the filter Fand amplified by the amplifier AM will actuate the loud-speaker LS. It is understood,

of course, that the filter F at B is tuned to pass current at the frequency of the current supplied by the generator G and modulated by M at location A. Vith the contacts 8 of locations A and B reversed then the apparatus at B will supply current from its generator Gr modulated by its modulator M to the conductor 2 which will flow in the closed circuit formed by the conductor, the distributed impedance and ground and current will now be induced in the coils 4, 5 and 6 of location A. With the filter F of location A tuned to pass current at the frequency of the generator G and modulated by M at B this current picked up by the inductor coils at A `will be amplified by the amplifier AM and made to actuate the loud-speaker LS or other indicating devices. With synchronized operation of the two contacts 8 an alternative exchange of messages can be carried on between the apparatus of locations A and B.

Fig. 5 shows diagr'ammatically a ytrack layout to which the conductor 2 as shown by dash lines is applied. This layout consists of the main tracks 12 and 13, Crossovers 14 and 15, siding 16 and aspur track 17. The distributed shunt capacitybetween the conductor 2 and -ground is .visualized in the drawings by showing condensers in dotted lines at several points. a Suppose a train with locomotive 18 Aand a caboose 19 occupies the main track 12 as indicated and that both the locomotive 18 and caboose 19V are equipped with apparatus as shownat A and B of Fig. 2, respectively. ,f During certain instances in the operation of my system the caboose apparatus will induce a current in the conductor 2 which flows in the conductor 2 towards the locomotive 18.l At the switch 20-there is a tendency for this current to pass along the conductor 2 for the siding 16 and then back to the conductor 2 for the main track 12 at ivi the switch 21 at the opposite end ofthe siding due to possible branches or loop circuits.

and thereby complete a short circuit loop that might prevent the control current from reaching the locomotive. For this reason an impedance 22 is connected in series with the siding conductor 2 and chosen of such value that the control current at switch 20 is approximately equally divided between the two parallel paths. That is to say atleast half of the current will flow along the conductor 2 towards the locomotive 18 from the switch 20. Again at the switch 23 of the crossover 14 an impedance 24V is yplaced in series with the conductor 2 through the crossover and chosen of such a value that the signal current flowing in the conductor 2 of the main track 12 will divide substantially 'equally between the path through the crossover 14, conductor 2 of track 13 and the crossover 15 back to the conductor 2 at the Caboose 19, and the pathv leading alongthe conductor 2 of track A12 to the locomotive 18. Thus by inserting the several impedances in the conductor 2 as shown in F ig. A5 a sufficient current will flow through the normal path to insure reliable operation of the system. The impedances 22, 24 and 25 may be resistances if desired, however, if the signal current is to be modulated at the voice frequencies so that the current in the conductor 2 has. a wide range of frequencies it would be better to use inductive reactance since it will then vary in impedance the same as conductor 2. At the end of the spur track 17 there is located an impedance 26 between the conductor 2 and ground of a value equal to that of say about live thousand feet of track. An alternate method for the spur track would be to connect conductor 2 directlyto ground at 2? and insert a resistance 28 in series with the conductor 2 at the switch 29 leading from track 18 to the spur 17.

Fig. 6 shows another method of arranging the conductor 2 through this track layout. Here the operation of each switch is made to actuate a common switch circuit controller 32 in the usual manner. Contacts of the switch circuit controller connect the conductor 2 to the route set up for traffic and disconnects it from other routes as wll be readily understood by an inspection of Fig. 6'. In this arrangement the end of the conductor 2 for the spurl track 17 is prei'ferabltv connected to ground directly since it wouldnot be connected to the main track of conductor 2 unless the switch 29 is set for the spur. In the case it is desired to operate on the siding 16 at a time when both switches 2O and 21 are set for the main track, shunt impedances 30 and 31 should be connected betweentlie conductor 2V for the siding 16 and ground near each switchy as shown in Fig. 6. Wlhile the arrangement shown in Fig. 5 will have less first cost thearrangement of 6 re-` sults in practically no lossof control current These two Figs. 5 and'6 will serve to illustrate how the special conductor 2 may be applied to track layouts involving crossovers, siding and spur tracks.

I will now pointl out how my system is made practically immune to the influence of currents in the traiiic rails and to foreign space magnetic fields. As stated above the coils 4 and 5 are to be mounted transverse to the trackway and at an angle tothe horizontal plane and just yabove the required clearance to the track, as shown in Fig. 1. When two equal currents flowyin the saine direction in two parallel conducto-rs such as the rails 1 and 1a, the linesv of flux follow-the so-called Gassinian ovals as Asketched about the rails in Fig 3. It will be noted that at `the halfway point between the two rails '1 and 1aM there exist substantially no magnetic flux. The oval lines 33 in Fig, 3 illustrate the boundary between the region .where the flux lines surround only one'rail and the re-y gion where they surround two rails. Itl will be recalled that the kconductor 2 is toA be located midway between the rails and thus it is placed at a point where it will haveapproximately no Y electromagnetic induction with the rails 1 and 1a carrying equal parallel currents andvrhence changes in these two currents will cause no voltage to be induced in the `conductor 2. No induced currentwill therefore flow in the .conductor 2 that might influence the coils 4 and 5. It will be further seen from Fig. 3 that the angle at which the coils 4 and l5l are mounted is such `that the axis of each windingis substantially at right angles to the average flux created by the parallel currents vflowing in, the ra'ls 1 ard 1a and hence no voltage will be induced in the coils 4 and 5 directly as a result ofthe parallel currents in the traffic. rails. It will appear from Fig. 3 that the locating of the coils 4 and 5 at a. point where no voltage will be induced in them bycurrent flowing in the trafhc rails in parallel is not critical as their positions can be vreadily adjusted both as to their horizontal distance from the center klire of the track and as to the angle at whichthey are mounted. v .i i,

.It follows, therefore, that coils 4 and 5 are positioned to be influenced by magnetic fields created by al current in the; conductor 2 indicated by the circular lines in 'F`v 3 and yet are so positioned as to be practically immune from the influence of the magnetic fields created about the trafiic rails the result of equa-l currents flowing in the saine direction in the two rails.- At the same time the position of the conductor 2 issuch that that might in turn influence the coils 4 and 5.

Fig. 4 shows the effect of a current flowing in opposite directions in the two trafrlc rails, such for example as the usual track circuit current. The dash lines with their arrows show the approximate direction of the flux lines for a given instant. It will be noted that these lines give small upward components asv represented by the lines l2 and 13 along the axes of the coils 4V and 5, respectively. No matter at what angle the axes of the coils 4 and 5 maybe so long as they are symmetrical with respect to the center line of the track these upward components represent the induction of the flux lines about the rails created by current flowing in opposite directions in the two rails and both will be either upward or both downward at any given 1'nstant. But the coils 4 and 5 are connected to add the voltage induced therein by current flowing in the conductor 2. rlhat is to say, coils 4 and 5 are aiding when the flux in one coil is upward and the flux in the other coil is downward at any given instant. It follows that the effect ef a current down one rail and back the opposite rail w`ll be cancelled by the opposing of the two equal induced voltages in the coils 4 and 5. It is to be seen, therefore, that the coils 4 and 5 are so connected as to be practically innnune from the electromagnetic fields created about the rails by a current flowing down one rail and back the opposite rail.

Any distribution of currents between the two rails may be considered as made u p of an equal current in the same direction in each rail and another current down one rail and back the other. In the foregoing discussion it has been shown that my system is balanced for either alone, and hence by the principle of superimposing of linear effects it is balanced for any combination of these currents. For example ten amperes in one rail and six in the other may be considered as `a parallel current of eight amperes in each rail and two amperes circulating down one rail and back the other. Again ten amperes in one rail alone can be considered as five am- 'peres in each rail in the same direction and a circulating current of five amperes.

Considering next a changing Vmagnetic field uniform in space, such for example as that which might be'creat'ed-bya transmis'- lsion line or nearby generator, the axes of' coils 4 and 5 will be each perpendicular to the component of the space magnetic field parallel with the track and hence they will have no induction with that component. To the vertical component of any space magnetic field the coils 4 and 5 are symmetrical and will oppose each other due to the fact that they are so connected that they add their effects when the induction of one is upward and that of the other downward at any given instant.

The coils 4 and 5 will have, however, induction with the mutually per endicular component of th-e space magnetic eld that is transverse to the trackway and the voltage induced in the coils 4 and 5 will be in a direction to add their effects. It is to balance out this component of the space magnetic field transverse to the trackway that the coil 6 is provided. Coil 6 is located symme trically with respect to the two track rails with its axis transverse to the trackway and is preferably placed in the same vertical plane as the coils 4 and 5. It will1 be recalled that the coil 6 is so connected in the circuit with the coils 4 and 5 that the voltage in# duced therein by current flowing in the conductor 2 op-poses the induction in coils 4 and 5 and for this reason is located at a considerably greater distance from the conductor 2 than the coils 4 and 5 so that its induction with 2 will be much less than either of the other coils. I prefer to so locate coil 6 that it does not reduce the normal value induced in the coils 4 and 5 by more than say twentyfive per c-ent which loss I have found can be sustained and yet have reliable operation of the receiving apparatus. On the other hand the transverse component of the space magnetic field will be substantially uniform for all three coils and coil 6 in this instance is in a position to be much mor-e effective than either coils 4 and 5 due to the fact that its axis is parallel to this transverse component. l propose to so proportion the windings of these coils, and the size of their cores, that the induction of coil 6 from this transverse component of the space magnetic field will be substantially equal to the combined induction of the coils 4 and 5 to the same component. By such proportioning of the coils the influence of the transverse component of the space magnetic field is balanced out. To this end coil 6 may be an iron core coil, the same as the coils 4 and 5, of proper section and number of terms to insure a balance. I prefer to employ an air core coil for coil 6 since it may then be built with a much lower factor and hence smaller power loss than an iron core coil. Coil 6 is not needed for sending and it may be switched out of circuit at that time with a resultant increase in the voltage induced in 2 Such a system as here disclosed is substantially immune to effects of any distribution of any currents in the two traflic rails and at the same time immune to the effects of any space-uniform magnetic field.

Although I have herein shown and described only certain forms of apparatus em` bodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

20 acterized by the fact that two of said wind- Having thus described my invention, what I yclaim is:

l. Train signaling apparatus including, three windings mounted on a train disposed 5 in inductive relation with a single trackway conductor characterized by the fact that two of said windings add their inductive eifects created by current flowing in said conductor while the third winding opposes, said third winding so positioned and proportioned as to cause but a'relatively small cancelling of the induction by current in the conductor while balancing out the induction of said iirst two windings due to any space-uniform magnetic lield. Y

2. Train signaling apparatus including, three windings mounted on a train disposed in inductive relation with a conductor located midway between the two traffic rails charings add their inductive effects created by current ilowing in the conductor while the third winding opposes, said two windings so positioned as to be practically immune to any distribution of current in the traffic rails.I while said third winding is so positioned and proportioned as to cause but a relatively small cancelling of the induction by current in the conductor while approximately balancing out the induction due to any space magnetic iield of foreign origin.

3. T'rain signaling apparatus including, threeV windings mounted on a train disposed in an inductive relation with a conductor extending along the trackway characterized by the fact that two of said windings add their inductive eects created by current flowing in the conductor while the third winding opposes, said windings so positioned and proportioned that there will be but a small cancelling by the said third winding of the electromotive forces induced in the windings by current in said conductor but that the electromotive forces induced in the windtrackway will be substantially balanced out. 4. Train signaling apparatus including. two windings mounted on a train disposed in inductive relation with a conductor lo- A cated midway between the two traiic rails, said windings connected in series in sucha manner that the electromotive forces induced therein by current flowing in the conductor are additive, and said windings so positioned with respect to the traiiic rails that they are approximately immune to the luxes created by any distribution of current in said traiiic rails.

5. Train signaling apparatus including, a conductor extending along each track of a railway and mounted on the ties to form with the distributed impedance between said conductor and ground and the ground path a closed circuit for signaling, and means asso- 5 ciated with Veach switch vleading from the the conductor. j

ings by fluxes from sources adjacent the` ance connected in'series with the conductor i for an auxiliary track leading from a switch of the main track to prevent the short-circuiting ot a portion of the conductor for the main track by the conductor for the auxiliary track.

7 Train signaling apparatus including, a conductor extending along each track of'a railway to form with the distributedimpedance between said conductorand ground and the ground path a closed circuit for' signaling, and means operated by each switch of the railway to connect the conductor the way the track is set up for trailic and to disconnect the conductor from other branches of 8. A control system Vfor railway trains including, a transmitting circuit and areceiving circuit at each end of the train; a closed trackway circuit comprising asingle conductor extendingV along the trackway, the

Vdistributed impedance between said conductor and ground and the ground path; an yinductor at each'end' of the trainV disposed in inductive 'relation to said conductor, means at each end of the train to connect the inductor at the same end to either the transmitting circuit or to the receiving circuit at that end of the'train, andv means for each l receiving circuit for amplifying the control signals transmitted from the opposite end of the train. f

` 9. Acontrolsystem for railwaytrains including, a transmitting circuitv and a receiving circuit' at each end of train; a closed trackway circuit comprising a single conductor extending along the trackway, theA distributed impedance between said conductor and ground and the ground path; three windings connected in series at each end'ot the train disposed in inductive relation with the said conductor and arranged to be substantially immune to the influence of mag tending between said two locations comprising a single conductor, the. distributed impedance between said con-ductor and ground and the ground path; three windings at cach location connected in series disposed in nductive relation with the conductor and farranged to be substantially immune to the influence of space magnetic fields created by nearby sources, and means at each location t-o connect the three windings .of a location to either the transmitting device or the receiving device vat the same location for communicating signals between the two locations. Y

11. A control system including, a transmitting -device anda receiving device at each of two spaced locations; a closed circuit extending between said two locati-ons comprising a single conductor, the distributed impedance between said conductor and ground and the ground path; three windings at each locationdisposed in inductive relation with said conductor and arranged that two of said windings add their inductive etl'ects produced byccurrent flowing in said conductor While the third winding opposes7 said windings so positioned and proportioned that there is buty a small cancelling by the said third winding of the electromotive forces induced in the windings by current in said conductor but the electromotive forces induced in the windings by fluxes from sources adjacent the conductor are substantially balanced out, andmeans at each location to connect the three windings of a location to either the transmitting device or the receiving device at that location for communicating signals between the two locations.

12. A control system for railways including, a single conductor extending yalong the trackway and positioned to be substantially immune to the influence of magnetic fields created by currents )flowing in the traffic rails, transmitting means for inducing in said conductor a signaling current which flows in both directions in the conductor from the point of induction and returns through the distributed impedance between said conductor and ground and the'ground path, and a receiving means responsive to current Howing in said conductor due to said transmitting mea-ns for controlling a signaling device.

13. A. control system for railways including, a single conductor extending along the traclrway and positioned to be substantially immune to the influence of magnetic fields created `by currents flowing in the traffic rails, transmitting means for inducing in said conductor a signaling current which flows in bot-h directions in the conductor from the point of induction vand returnsthrough the distributed impedance between said conductor and ground and the ground path, and a receiving means including a pair of wind- PAUL N. Bossinfr. 

